I agree that they are expensive.
We have recently returned from a 4 night stay at the C&CC site at Sandringham which cost about £78. For the same period the cost at the adjacent CMC site would have been £85.
I accept that the electricity charges now account for about £5 per 24hrs but these charges are pricing us out of the market.
If our health was better we would be heading south by now.

I use a CoPilot Caravan on and iPad but it will work on a phone or android pad. I wrote a little about it, it may be suitable for you. I think they allow a free months trial.
http://wandering.me.uk/copilot/

I fitted a solar roof panel primarily to keep our battery charged when the van is in storage. This has been very successful and the fact that we can now also go off-grid when we wish is a bonus.
http://wandering.me.uk/solar-charger/

I wrote a list that may be of some help: http://wandering. me. uk/the-bare-essentials/
Don't for get that you are supposed to be enjoying the adventure, there will be times when you doubt your sanity, but it passes. The advice to make you first site close to home so that you can go and get the bits you didn't bring is also good.

I have fitted a 100w semi-flexible panel to our Lunar Clubman roof, it is stuck on with Sika Flex 552 flexible adhesive.
I followed the panel suppliers recommendation by putting a thick bead of adhesive, about 6mm thick in a zig-zag patten on the roof and laid the panel on that with light pressure. This resulted in a strong bond with a small air gap under the panel. There is no sign on the panel moving.
If I need to remove the panel I anticipate little difficulty in doing so by cutting through the adhesive with a thin wire used in the style of a cheese-wire cutter.
I describe the installation on my website, address below and hope that is of help.